EMF Measurement Procedure Overview
How to make accurate electromagnetic field & power line surveys
EMF/EMR MEASUREMENT OVERVIEW - CONTENTS: An overview of the procedure for making accurate EMF electromagnetic field strength measurements & surveys. Sources of error and variability in electromagnetic field strength measurement surveys; EMF exposure levels for electrical workers
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Overview of how to measure EMF exposure levels & field strengths: this paper provides an overview of the recommended procedure for performing electromagnetic field (EMF) or
electro-magnetic radiation EMR measurements either by engaging a professional or by consumers using low-cost instruments
which measure EMF exposure levels in gauss or milligauss.
An Overview of an EMF/EMR Measurement Survey Procedure
Because RF and EMF measurement tools need to be properly chosen to measure the particular type and frequency of RF or EMF signal that is of interest, be sure to also see EMF RF FIELD & FREQUENCY DEFINITIONS for a simple explanation of different types of radio frequency (RF) and electromagnetic frequency (EMF) types and where they are found.
Magnetic fields are directional; measurements are affected by position as well as location of the instrument within the area being examined, and by the
distance of the instrument from the field source. Our field experience
strongly suggests that results are quite variable depending on the particular
direction aimed and positions held when using the measuring instrument.
Therefore, and consonant with recommendations from the manufacturers, each of
our "measurements" is derived from at least three instrument readings, holding
the instrument pointed at a suspected field source (e.g. nearby power line),
pointed straight up, and held horizontally. Horizontal and vertical
measurements are recorded as the highest obtained following a 360 degree scan
of the area with the instrument held in that position.
During such a rotation in the presence of a strong magnetic field we find
reading levels ranging widely.
We warn that measurements made by another
professional will not duplicate our results unless our exact procedure is used
with an instrument of similar performance at the identical locations. However
our experience is that measurements with similar instruments in approximately
the same locations and circumstances, produce results which are quite close.
For each instrument reading we record location, position, meter sensitivity
settings, meter readings, and estimated distance to the suspected field source,
if any. We also record observations of devices such as TV's or computers if
they are seen operating nearby.
For the analog device measurements, actual meter readings are converted to
milli/microgauss using tables provided by the instrument manufacturer based on
the sensitivity range to which the instrument was set at time of use.
of sensitivity settings are required to protect this very delicate instrument
from being damaged by the fields being measured. The manufacturer describes a
mathematical procedure which we follow to combine these data into a single
field level number for an area being measured.
For the digital device measurements, actual measurements are read on the
instrument in gauss or milligauss, depending on a field strength sensitivity
selection on the meter.
As with any potential poison, our concerns are first to establish a dose-relationship to effects of
the poison, and next to establish a reliable way to measure the actual dose or exposure that a person
Electrical Utility Workers and EMF Exposure
It's apparent that electrical utility workers, especially people who spend a good part of their working day up close to power transmission lines and electrical power stepdown transformers are likely to have higher exposure to electrical fields and EMF than occupants of a typical residential building.
We recommend close monitoring and scrutiny of the soundness of studies that are performed to examine the health effects of EMF exposure for this population.
See Radio Frequency RF Detection Meters This article describes several low-cost and accurate radio frequency or RF detection and measurement devices suitable for radio, TV, cellphone, microwave, and similar signals.
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Questions & answers or comments about the basic approaches to measuring the level of exposure to EMF electromagnetic fields in the home or workplace.
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"Questions and Answers about Biological Effects and Potential Hazards of Radiofrequency Electromagnetic Fields", Federal Communications Commission, Office of Engineering and Technology, US FCC, OET Bulleting 56, 4th Edition, August 1999
" Many consumer and industrial products and applications make use of some form of
electromagnetic energy. One type of electromagnetic energy that is of increasing importance
worldwide is radiofrequency (or "RF") energy, including radio waves and microwaves, which
is used for providing telecommunications, broadcast and other services. In the United States
the Federal Communications Commission (FCC) authorizes or licenses most RF
telecommunications services, facilities, and devices used by the public, industry and state and
local governmental organizations. Because of its regulatory responsibilities in this area the
FCC often receives inquiries concerning whether there are potential safety hazards due to
human exposure to RF energy emitted by FCC-regulated transmitters. Heightened awareness
of the expanding use of RF technology has led some people to speculate that "electromagnetic
pollution" is causing significant risks to human health from environmental RF electromagnetic
fields. This document is designed to provide factual information and to answer some of the
most commonly asked questions related to this topic." - original source: U.S. Federal Communications Commission Office of Engineering and Technology, http://www.fcc.gov/Bureaus/Engineering_Technology/Documents/bulletins/oet56/oet56e4.pdf
"Magnetic Field Exposure and Cancer: Questions and Answers [ copy on file as /emf/EMF_Fact_Sheet_NCI_NIH.pdf ] - ," National Cancer Institute, U.S. National Institutes of Health, web search September 2010, original source: http://www.cancer.gov/cancertopics/factsheet/Risk/magnetic-fields
makes these five key points about EMF
Electric and magnetic fields (EMF) are areas of energy that surround any electrical device. EMFs are produced by power lines, electrical wiring, and appliances (see Question 1).
Electric fields are easily shielded or weakened by walls and other objects, whereas magnetic fields are not. Since magnetic fields are more likely to penetrate the body, they are the component of EMFs that are usually studied in relation to cancer (see Question 1).
Overall, there is limited evidence that magnetic fields cause childhood leukemia, and there is inadequate evidence that these magnetic fields cause other cancers in children (see Question 2).
Studies of magnetic field exposure from power lines and electric blankets in adults show little evidence of an association with leukemia, brain tumors, or breast cancer (see Question 3).
Past studies of occupational magnetic field exposure in adults showed very small increases in leukemia and brain tumors. However, more recent, well-conducted studies have shown inconsistent associations with leukemia, brain tumors, and breast cancer (see Question 4).
US Environmental Protection Agency, Office of Pesticides
and Toxic Substances, TSCA Assistance Office (TS-799), 800-424-9065
"Evaluation of Potential Carcinogenicity of Electromagnetic Fields,"
EPA Report #EPA/600/6-90/005B October 1990. EPA: 513/569-7562.
"Biological Effects of Power Frequency Electric and Magnetic Fields"
background paper, prepared as part of OTA's assessment of "Electric Power
Wheeling and Dealing: Technological Considerations for Increasing Competition,"
prepared for OTA by Indira Nair, M. Granger Morgan, H. Keith Florig, Department
of Engineering and Public Policy, Carnegie Mellon University, Pittsburgh, PA
"Biological Effects of Power Line Fields," New York State Powerline
Project. Scientific Advisory Board Final Report, July 1, 1987.
"Extremely Low Frequency (ELF) Fields," Environmental Health
Criteria 35. World Health Organization, Geneva, 1984.
"Electric and Magnetic Fields at Extremely Low Frequencies:
Interactions with Biological Systems. In: Non ionizing Radiation Protection,
World Health Organization, Regional Office for Europe, Copenhagen, 1987.
"Electric and Magnetic Fields from 60 Hertz Electric Power: What do
we know about possible health risks?," Department of Engineering and Public
Policy, Carnegie Mellon University, Pittsburgh, PA 15213 1989.
"Electromagnetic Fields Are Being Scrutinized for Linkage to
Cancer," Sandra Blakeslee, New York Times, Medical Science section, April
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